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In probability and statistics, a probability distribution assigns a probability to each measurable subset of the possible outcomes of a random experiment, survey, or procedure of statistical inference.

4 votes

on the difference of exponential random variables

No. Consider an analogous question for the random variables $Z_1$, $Z_2$ uniformly distributed on $\lbrace0,1,2,3\rbrace$ whose sum has the probabilities $1/16, 2/16, 3/16, 4/16, 3/16, 2/16, 1/16$ of …
Douglas Zare's user avatar
6 votes
Accepted

Distribution of Maximum of a uniform multinomial distribution

The probability that there is at least one bin with at least $c$ items is less than or equal to the expected number of bins with at least $c$ items, which is $k$ times the probability that a particula …
Douglas Zare's user avatar
2 votes

Random partitions with prescribed pairwise membership probabilities

There are many more partitions than there are pairs for large enough $n$, so rank-nullity says uniqueness will fail. $\frac12 (12) + \frac12 (34) \sim \frac12 (12)(34) + \frac12 e$ where we identify …
Douglas Zare's user avatar
5 votes
Accepted

Minimum probability that two Gaussian random variables are small

The minimum value is simply $2\alpha-1 = 0.365379$ where $\alpha = \Phi(1)-\Phi(-1) = P(|X|<1)$ where $X \sim N(0,1)$. This can be achieved by translating the percentile of $X$ (considering the percen …
Douglas Zare's user avatar
2 votes

A generalization of negative binomial distribution

This is related to the coupon-collector problem. These random variables have been studied by many people, although I don't recall a particular name for them. See, for example, Anna Pósfai's thesis (ab …
Douglas Zare's user avatar
5 votes

Does bounding moments make distributions close in total variation distance?

No, you need some other condition if you want to restrict the total variation distance. The total variation distance is maximal between a discrete random variable and a continuous one, and you can tak …
Douglas Zare's user avatar
1 vote

Comparison of tail behaviour of two (bounded) random variables given their moments

First, here is a counterexample to a simpler statement with $a_0$ fixed at $0$: Let $Y$ be the constant random variable $2$. Let $X$ be $1$ with probability $1/2$, and $3$ with probability $1/2$. Then …
Douglas Zare's user avatar
2 votes

How do you call the problem of approximating a continuous distribution with a simple discret...

It sounds like you want evenly spaced quantiles of a distribution. If you have to represent a distribution with one number, the median may be a reasonable choice. If $n=9$, then you can use the $10$th …
Douglas Zare's user avatar
7 votes

tight bounds on probability of sum of laplace random variables.

You can read off the density function as follows: Since a Laplace distribution with mean $0$ is the difference of two IID exponential distributions, the sum of $n$ IID Laplace distributions with mean …
Douglas Zare's user avatar
3 votes
Accepted

divisibility of uniform distribution

Here is a direct argument. Suppose independent $X_1,X_2 \sim X$, and $X_1+X_2$ is uniform on $[0,1]$. $X$ is supported on $[0,1/2]$. For any $0 \lt \alpha \lt 1/4$, $\alpha = P\left(X_1+X_2 \in [ …
Douglas Zare's user avatar
7 votes
Accepted

Number of intervals needed to cross, Brownian motion

I'll address the second question on the expected value of the sum $K_n$. Let $\phi(x)$ and $\Phi(x)$ be the probability density function and cumulative distribution functions for a standard normal di …
Douglas Zare's user avatar
4 votes

Brownian motion, crossing intervals, possible usage of second moment method?

Here is some notation I used in the related problem with some results. Let the probability hat a Brownian motion starting at $0$ returns to home on $[a,b]$ be $h(a,b) = h(b/a)$. By the calculation in …
Douglas Zare's user avatar
6 votes

Should you bet in poker against Darth Vader?

Getting all-in while behind It is not just when you are ahead that you might want to get all-in against someone who has an information advantage. Suppose the pot is $1$ and the effective stack depth …
Douglas Zare's user avatar
3 votes
Accepted

Should you bet in poker against Darth Vader?

Here is an answer to the updated question: Suppose that there are two betting rounds. Darth Vader has three types of hands. Type 1 wins with probability 1. Type 2 is a draw that hits (becomes a winni …
Douglas Zare's user avatar
7 votes
Accepted

The average number of people that can sit on a bench of a given length.

Assume that the process stops when someone can't fit. I believe the distribution of the amount of overshoot is known as a ladder height distribution, and that this is in Feller's classic text, but I …
Douglas Zare's user avatar

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